CDL Air Brakes TestInspecting Air Brake SystemsEasy
During a pre-trip inspection of an air brake system, a driver notices that the air compressor is cycling on and off more frequently than usual, even when there are no significant air leaks. What could this frequent cycling indicate?
- AThe air tanks are overfilled, causing the compressor to relieve excess pressure.
- BThe air pressure gauge is inaccurate, showing incorrect readings.
- CThe air dryer is malfunctioning and not removing moisture effectively.
- DThe governor is set too low, causing the compressor to cut in and out prematurely.
Show answer & explanationAnswer & explanation
Correct answer: D. The governor is set too low, causing the compressor to cut in and out prematurely.
Frequent cycling of the air compressor without significant air loss often indicates an issue with the governor's settings. If the governor is set too low, it will cause the compressor to cut in at a lower pressure and cut out at a lower maximum pressure, leading to more frequent cycling.
Why the other options are wrong
- A. Air tanks cannot be 'overfilled' in a sealed system; the governor regulates the maximum pressure.
- B. An inaccurate gauge would show incorrect readings but wouldn't directly cause the compressor to cycle more frequently unless the actual pressure was fluctuating rapidly.
- C. A malfunctioning air dryer would likely lead to moisture in the system, not necessarily frequent compressor cycling.
Air Compressor Governor
The governor controls when the air compressor pumps air into the air storage tanks. It has a 'cut-in' pressure (compressor starts) and a 'cut-out' pressure (compressor stops).
- Regulates air pressure in the tanks.
- Cut-in pressure typically around 100 psi.
- Cut-out pressure typically around 125 psi.
Memory trick: Governor's Gaze: Too low, it'll go-go-go!